The present invention relates to a communication control system of fluid control valves in which control signals are transmitted from a central unit to a plurality of terminal units by an optical fiber link, thereby remotely controlling the fluid control valves.
Hitherto, as a system for remotely controlling a plurality of fluid control valves provided on the sides of terminals by a sequence controller or the like, such a system as shown in, e.g., FIG. 1 has been known.
In FIG. 1, reference numeral 100 denotes a control unit using a programmable sequencer or the like. Signal lines are connected from the control unit 100 to solenoid valves 104 of a plurality of terminals 102, and control signals are supplied from the control unit 100 to the solenoid valves 104 through the signal lines. Further, each terminal 102 has a limit switch 106 to detect the operating states of terminal apparatuses such as actuator, valves, and the like by the solenoid valve 104. In order to display the operating states of the terminal apparatuses by the control unit 100, each of the limit switches 106 of the terminals 102 is connected to the control unit 100 by a signal line.
However, in such a conventional remote control system, the control unit 100 is connected to the solenoid valves 104 and limit switches 106 provided for a plurality of terminals 102 by the signal lines, respectively. In general, for example, the sequence controller can connect fifty to hundred terminals 102. Therefore, the number of signal lines including the signal lines to connect the limit switches 106 is very large. Thus, the works to install the signal lines when the system is set become hard and the costs increase.